This revised proposal requests funding for continuation of support of the training program in Pediatric Infectious Diseases that is currently 5 years old. This discipline is important in promoting understanding of pathogenesis, antibiotics, antivirals, vaccines, and other anti-infectives in a setting of transplantation, chemotherapy for malignancy, and emerging infections, and assuring that there continue to be new developments in the field. The aim of the program is to develop MD investigators, who are already trained in Clinical Pediatrics, who aspire to a career in research, public health, and/or teaching. The program is an interdisciplinary one involving not only investigator-trainers in the Department of Pediatrics, but also those in the Departments of Microbiology, Anatomy and Cell Biology, Epidemiology, Public Health, Medicine and Immunology. There will also be an opportunity to gain experience in clinical trials as well as hospital microbiology, epidemiology and infection control during clinical rotations; however, 80% of training will be devoted to research. The period of training will be for 3-4 years; support for 3 Postdoctoral Fellows annually is being requested. Extensive resources at Columbia University are available to postdoctoral fellows, including seminars given by outstanding speakers, and teaching and mentoring from an experienced group of well-funded Pediatricians trained in the discipline of Infectious Diseases. These core clinician-scientists have already linked to distinguished basic scientists at Columbia and they collaborate extensively with each other in research projects. These scientists are currently investigating infectious organisms and examining the molecular pathogenesis of disease; the basic science perspective provides powerful insights into understanding the means by which pathogens evade host defenses and establish and continue infection. The core group of pediatrician-trainers includes 6 full-time academic faculty members, all actively carrying out well-funded research programs ranging from basic science to epidemiology, vaccine development, clinical trials of anti-infectives and vaccines, and hospital infection control. The renewal of this training grant will enable us to continue a training program that has so far been highly successful at this University during the past 5 years.